Subaqueous system of artillery fire adjustment



April 25, 1933. B, J'Q 1,905,315

S UBAQUEOUS SYSTEM OF ARTILLERY FIRE ADJUSTMENT Viled Jan. 9, 1-925 -2 Sheets-Sheet 1 PriIZS, 1933. E. s. STEPHEN$ON 1,905,315

SK JBAQUEOUS SYSTEM 0F ARTILLERY FIRE ADJUSTMENT Filed Jan. 9, 5 2 Sheets-Sheet '2 ,Batented Apr. 25, 1933 NT oFiE EDWARD 1B. STEPHENSON, OF WASHINGTON, DISTRICT OF COLUMB Application filed January 9, 1325. Serial No. 1,510. I

(GEAMED UNDER THE ACT OF MARCH 3, 18 83, AS AMENDED APRIL 80, 1928; $70 0. 75?) This invention described herein may be manufactured and used by or for the Government for governmental purposes, without the payment to me of any royalty thereon.

5 This invention relates to a subaqueous system of artilery fireadjustment, utilizing water as a transmitting medium, the impact of the projectile striking the water as a source pulse and hydroof the pressure 'wave or phones as detectors.

' One of the principal objects of this invention is to effect a new and improved system of subaqueous artillery ranging automatically functioning to furnish data necessary to aflord a rapid determination. of the range and an aeurate adjustment of the artillery Another important object of this invention is to provide a system which, owing to its electro-mechanical character, will enable a rapid and accurate determination of the range, irrespective of prevailing atmospheric conditions, darkness, and errors of observation, factors which heretofore tended to serious inaccuracy and materially hampered op.-

erations. This invention is based on the theory that- (1) a projectile striking the water produces a pressure pulse or wave having acircular so wave front and capable of traveling with uniform velocity and without distortion over long distances, (2) there is a time interval between the arrival of the pressure wave or pulse at t 0 or more stations located at defi- 85 nitely. known and unequally distant points, (3) the diflerences in the time of arrlval at the different stations, taken in connection with the constant, known rate of'propa ation of the pressure wave in water will ena le 40 determination of the source of the disturbance, (4) the source of the pressure wave, likewise the position of the target, being known the correct artillery adjustment canreadily be ascertained.

In the acompany drawingsin which corresponding parts are indicated by similar reference characters:

Fig. 1 is a diagrammatic view illustrating a fragment of a coast line, a coast defense battery consisting of a series of forts, a centrol zone of fire, the practical lateral limits of such fire and a plurality of suitably located hydrophone detector stations.

Fig. 2 is a diagrammatic view illustrating a fragment of coast line, a series of suitably submerged detectors, a central station, the receiving sets at the central station and theirelectrical connections with the detectors. I

Fig. 3 is a transverse vertical section ofa type of hydrophone used in connection with this invention.

b Fig. 4 is a trigonometrical diagram for use in explaining the method used in determining the unknown source of the pressure wave.

Fig. 5 is a diagrammatic view illustrating one of the submerged microphones, its indicia and anchorin arrangement. A

Fig. 6 is a iagrammatic view illustrating the application of the stringed galvanometer to the optical system and photographic recording means used therewith.

In the present system of artillery ranging, observations concerning the result of the artillery fire are made from elevated positions on land or from aerial outposts in the nature 1 of airplanes or balloons, the observer transmitting his observations by manual signalling, wireless, or telephone, dependent on the exigencies of the situation, to the battery commander who then makes the necessary corrections for adjustments of fire. I

Manifestly the accuracy and eflicien'cy of this system are largely governed by the ability of the observer, atmospheric conditions, darkness, etc. and while answering the purpose in the absence of a superior system, are far from satisfactory. It is therefore the aim and purpose of this invention to provide a system which is largely automatic in its operation, and not dependent on or in any wa influenced by the factors specified.

riefiy stated, this invention consists in producing a characteristic pressure wave or pulse, through the instrumentality of a pray jectile striking the water, determining the origin of the pulse, lotting the course of a moving target, and t en corelating the pulse origin withthe location of the target to obtain the range adjustment. y

I By locatingthe detectors in this manner, :00

. relation of such disturbances to the target,

can be quickly determined, assuming the posltionof the target is known.

In order to facilitate the discussion of this invention, it will be further considered under the following headin sz-Detector installation, Central statlonl, Mathematical determination of the source of the pressure wave, Plotting or tracking the course of the target, and Conclusion v In the illustrated embodiment of this invention there is shown, for descri tive purposes a portion of a coast line a coast ortification B, consisting of three artillery batteries C, the latter having a central zone of fire indicated by the area D, and a practical lateral limit of fire shown by the radi- :11 lines E.

Detector installation When a projectile strikes the water a pressure pulse is generated, characterized by its ,brief duration and extensive amplitude. To locate the source of this pressure wave or pulse a plurality of hydro hone detector stations, six in number, an M3, M3, M4, M5, arld M5, are Submerged 0 shore at a distance suflicient to avoid water noises on shore and 'aiiord an uninterrupted water path between the stations and the source of the pressure wave. 7

' These stations are positioned in the arc of a circle and at equal distances a rt,.the chord of the arc corresponding to e radius F, of a circle having its center located at the point of maximum accuracy G, in the central zone of fire D. p

The hydrophone detector stations used with. this invention are of special designand embody a microphone button 1, mounted interior of a mine casing 2. suitably anchored as at 3; the position of e mine casing being shown by a suitable float 4, which i dosir-able may beprovided with a signal flag or the like.

The microphone button 1, consists essentiall of two polished graphite plates 5 and lacedfparallelto one another and eeps P ai'ated about the intervening space being partially filled with fine carbon granules.

One of theplates is attached to a diaphragm allowing it to vibrate back and forth along a line perpendicular to its surface to alternatingly compress and release the carbon granules. This movable. plate is rigidly atgalvanometer,

indicated ME tached as at 6 to a suitable mounting with the casing as shown in Figure 3.

The motion of the diaphragm produced by the action of the pressure wave causes correspondin changes in the pressure between the car on granules, varies the resistance in the primary circuit of the transformer and actuates the galvanometer and other apparatus at the central station to produce a record of the wave.

Oentral station The several detectors are connected to a receiving set, located at the fortification and referred to as a central station. Each set includes a batte circuit 7, also a rimary coil 8 of a trans ormer 9, the secon ary coil 1% Galvanometer 11, is of special design op-' erating onthe principle that a wire carrying a current through a magnetic field will be deflected in a plane perpendicular to the direction of the wire and that of the magnetic field. The wire may be of platinum or tungsten and is approximately .0004 in diameter. Underthe proper tension such a wire will follow closely the variations in the im-' pressed electro motive force for all ordinary frequencies. This is an important feature necessary to insure that the record obtained will be as characteristic of the original pressure wave as the apparatus will permit.

To secure a permanent record of the vibrations of the galvanometer strings, as well as the time of such vibration, shadows of the strings are cast upon a 1 movable photographic film by a suitable optical arrangement,-designated 12 in Fig. '6: hence any movement of the strings will be reproduced on the film.

To obtain the exact time the indications are received, a further mechanism in the nature of a revolving disk 13, synchronized with a tuning fork casts thin transverse shadows acrossthe film record at 1/100 second intervals, with thicker shadows every second,

The galvanometer, recording and timing apparatus just described are fully discussed I 7 that the disturbance produced by the impact of'a p'.ojectile striking the openjwater is a pressure pulse or wave characterized as stated, and that the time inter- .vals elapsing between the arrival of the impulse at three or more stations suitably spaced are known, the ori in of the disturbance can readily be locate i.

" Consider twostations such as M and M the. latter including a galvanom'eter is the locus of a point which moves so that the difference of its distances from the foci is constant.

Referring to Fig. 4, if M and M are two hydrophone stations, L the distance .be-

tween M and M and ROW a circle circumscribed about M as a center with radius ZT1) where V is the velocity of the pressure wave in water, the hyperbola XC' will be the locus of the centers of the circles which touch the circle ROW and pass through M i If the origin of the pressure wave is at a distance which is large compared with the distance M M the arc OM of the wave front approximates a straight line and in the limit will be a straight line passing through M and touching the circle whose center is M while the origin of the pressure wave will lie in the perpendicular bisector of the tangent 0M V The perpendicular bisector of the tangent willtpass through the middle point of the line M M and will touch the hyperbola considered above at infinity. It is therefore the asymptoteof the hyperbola.

For practical purposes, in the graphical location of the origin of the pressure wave on a plotting board, it is highly desirable to plot asymptotes, which are straight lines, rather than hyperbolae. We may therefore establish a relation between L the distance between the hydrophone stations M and M the time diflerence t between the times T and T of the arrival of the wave atM and M respectively, and 0 the angle between the perpendicular bisector of the line M M il the asymptote XC of the hyperbole In the figure angle oM Mg 114,114 L 12 mm sin 91:

ting boardi'n such a way that if the centcr' of the base is laid on the division of said scale corresponding to the observed time interval at the string is the asymptote of the hyperbola in which the origin of the pressure wave lies. The intersection of two or more such I this invention two I ployed, corresponding to the area previously strings would locate the point on the plotting board.

Plotting) or tracking the course of the target For the purpose of this invention, any of the prevailing visual methods of plotting the course of a vessel may be employed, but in order to render the ystem entirely automatic and obtain the required data as quickly as possible, it "has been found advantageous to employ at least two water stations connected by multiple conductor cable'to two shore stations. leach water station embodies two or more hydrophones mounted on, a heavy tripod, which rests on thesea bottom, the hydrophones being suitably separated to form a base line. The location of the midpoint of the base line and its orientation are accurate ly known and the stations are disposed so that the perpendicular bisectors of the base lines will intersect at a wide angle in the vzone of fire. Each of the shore stations include a suitable supply of electrical power, the necessary switching apparatus and an accoustic or electrical compensator.

In the use of this apparatus the operator listens to the continuous noise produced by the propeller of the ship and transmitted through the water. If the location of the ship coincides with the line of the perpendicular bisectorof the base line, the sound appears to be directlyin front of the listener. On the other hand, should the oundappear to emanate from a point other than directly in front of the operator, the latter rotates the compensator until thesound appears directly in front and reads the index of the compensator when a time interval bell is sounded.

y previous calibration a scale can be made for the compensator, giving the angular deviation of the sound source from theperpendicul-ar base line of the water station. Intersections from two or more water stations give the location of the ship, on'the plotting board and consecutive readings its course or track.

The preceding arrangement forms no part of the present invention and is recited merely to illustrate the various steps incidental to the method under consideration.

In the practical application of one type of plotting boards are emindicated as the zone of fire, each: of the boards being suitably sub-divided according to the requirements of the problem. On one board, -by means of the agencies described,

the course of the targetis plotted on another is indicated the location of the origin of the pressure wave, hence; determination ofthe requisite artillery adjustment thus becomes a simple mechanical proposition corelating the location of the source of the pressure wave as shown on one plotting board with respect to the position of the target on the other.

C'onchwz'on In conclusion, it may be said, the proposed system provides an ideal solution of the problem of artillery fire adjustment, and possesses advantages in the nature of speed and accuracy not found in any of the existent systems, and this is especially true with respect to ranging in air, because:

I be accurately determined and will be perpen dicular tothe hydrophone base where its effeet in causing error will be a minimum- 5. The elimination of interference is sime 'pler 'becausethe hydrophone is practically unafl'ected by sounds in the air.

that if a shell enters the water ten miles from "the farthest microphone on the base, 11 seconds will berequired for the pressure wave to reachsuch microphone, 6 seconds for the development of the film, 18 seconds to read the latter, and '10 secondsto report results,

which thus gives. a permanent record .in

seconds. I I a In view of the foregoing, it. is evident this invention provides a simple, eflicient and expeditious method for accurately determining the range of a target,-as well as asystem by which the time of flight and range of a proent is:

jectile may be rapidly ascertained, since the principles underlying both problems are substantially identical.

Having defined my invention, what I claim as new and wish to secure by Letters Pat- 1.'A method of subaqueous artillery fire adjustment comprising utilization of the pulse generated by a "projectile striking a fluid medium, to determine the point of projectile impact.

2. A method of subaqueous artillery fire adjustment comprising production of a pulse in a liquid medium and utilization of such pulse to determine its point of origin.

3. A method of subaqueous fire adjustment comprising production in a fluid medium of a pulse characterized by its duration and amplitude and utilization of such pulse to determine its origin.

4. A method of subaqueous artillery fire adjustment comprising determination of the point at which an object enters a fluid medium by utilization of the resulting characteristic pulse.

5 method of subaqueousartillery fire ad ustment comprising the determination of normal wind velocity,

I adjustment consisting in acterlstic pressure pulse by means ofanob- Tests made with this system have shown utilizing the resulting pressure I acteristic pressure pulse through the instrumentality of an object striking a fluidmedium utilizing this pulse .to ascertain its origin and 'corelating the point of pulse origin with reference to a target of known location. 8. A method of subaqueolls artillery fire ject striking a fluid medium, utilizing this pulse to obtain the point atwhich the object contacted with the fluid medium, and corelatingsuch point with reference to a target of kno'wn'location. g c

'9. A method of, subaqueous artillery fire adjustment consisting in producing a char- I acteristicpressure pulse by means of a proectlle striking'a fluid medium,utilizing the resulting pulse to ascertain the point of impact, plotting the course of a'moving target. and 'corelating the point of impact, with ref-' erence to the location of the target to effect an adjustment of artillery fire.

10. A method of subaqueous artillery fire adjustment consisting in producing in a liquid medium a pulse characterized by its duration and amplitude, utilizing such pulse .to determine its origin, plotting the course of a moving target and corelating the point of pulse origin with reference to the location of target to effect an adjustment of artillery fire.

s5 producing a charno i 11. A method of subaqueous artillery fire adjustment consistsing in producing a characteristic pressure pulse, determining its origin, plotting the course of a moving target, and then corelating the point of pulse origin with the location of the target to efiect adjustment of artiller fire.

12. A method of suhaqueous artillery fire adjustment consisting in producing a characteristic pressure pulse, determining its origin, ascertaining the exact location of a moving target and then corelatirrg the point of pulse origin with reference to the location of the target to eflect an adjustment of artillery fire.

13. A adjustment consisting in producing a pressure pulse characterized by its duration and amplitude, ascertaining the exact location of a moving target and then corelating the point of pulse origin with reference to the location of the target to efiect an adjustment of artillery fire.

14. A method of subaqueous artillery fire adjustment consistin in producing a characteristic ressure p se by means of a projectile st g a fluid medium, determining the origin of such pulse, plotting the course of a moving target and then corelating the point of pulse origin with reference to the location of the target to effect an adjustment of artillery fire.

15. A method of subaqueous artillery fire adjustment consisting in generating a characteristic pulse through the instrumentality.

of a projectile striking a fluid medium and determining the point of pulse origin with reference to a target of known location.

16. A method of subaqueous artillery fire adjustment consisting in utilizing a characteristic pulse through the instrumentality of a projectile striking a fluid medium, plotting the course of a moving target, and determin-- ing, the point of pulse origin with reference to the location of the targetto effect an adjustment of artillery fire.

17 A method of subaqueous artillery fire adjustment consisting in producing a pres-v sure pulse characterized by its brief duration and amplitude, indicating the arrival of such pulse at a series of stations, measuring the difference in time of arrival at several of the stations and employing this data in connection with the known rate of pulse travel in a liquid medium to determine the point of pulse origin with reference to a target of known location. j

18. A method of subaqueous artillery fire adjustment consisting in producing a characteristic pressure pulsethrough the instrumentality ,of a. projectile striking a fluid medium, indicating the arrival of 'such pulse at a series of stations, measuring the difference-in time of :arrival at several of the stations, and employing this data in connection with the known rate of pulse travel in a liquid medium to determine the point of pulse origin with referenceto a target of known location;

19. A method of subaqueous artillery fire adjustment consisting in producing a characteristic pressure pulse through the instrumentality of projectile impact with a fluid medium, indicating the arrival of such ulse at a series of stations, measuring the difference in time of arrival at several of the sta- P tions, employing this data in connection with the known rate of ulse travel in a liquid medium to determine the point of, pulse origin, plotting the course of a moving target, 'and'then corelatin the origin of the pressure pulse with re erence to the location of iiaih e target to elfect an adjustment of artillery e. 20. A method of subaqueous artillery fire adjustment consisting in producing a charlocation.

21. A method of subaqueous artillery fire adjustment consisting in producing a characteristic pressure pulse by means of 'projectile impact witha fluid medium, indicating the arrival of such pulse at a series of submerged detector stations, measuring the difference in time of arrival of the pressure pulse at three or more of these stations, and employing this data in connection with the known rate of pressure pulse travel in a liquid medium to determine the point of pulse origin, plotting the course of a target, and corelating the point of pulse origin, with reference to the location of the target to effect an adjustment of artillery fire.

22. A method of subaqueous artillery fire adjustment consisting in producing a pressure pulse characterized by its brief.duration and extensive amplitude, indicating the arrival of such pulse at a series of submerged detector stations, the latter being arcuately arranged and located at equal distances apart, measuring the difference in time of arrival at several of the stations,'and employing this data in connection with the a known rate of pulse travel in a liquid medium to determine the point of pulse origin with reference to a tar et of known location.

I 23. A method 0 subaqueous artillery fire adjustment consistin in producing a pressure pulse characterlzed by its brief duration and extensive amplitude, indicating the arrivalof such pulse at a series of submerged detector stations, the latter being arcuately arranged .and located at equal distances apart, measuring the difference in time of arrival at several of the stations,employing this data in connection with the known rate of pulse travel to determine its point of origin, plotting the course of a moving tar get and then corelating the origin of the pressure pulse with reference to the location of'the target to eflect an adjustment of the ulse. 24. A method of subaqueousartillery fire adjustment consisting in producing a pressure pulse characterized by its brief durationv and extensive amplitude, indicating the arrival of such pulse at; a series of submerged detector stations, the latter being located at equal distances apart and arranged in the arc of a circle whose center coincidesfwith the adjustment consisting in fire, measuringthe difference in time of arrival at three or more of these stations, and employing this data in connection with the known rate of ulse travel in a liquid medium to determine t e point of pulse origin with reference to a target of known location.

25. A method of subaqueous artillery fire adjustment consisting in roducing a pressure pulse by means of pro ectile impact with a liquid medium, such impulse being characterized by its brief duration and extensive amplitude, indicating the arrival of this pulse at a series of submerged detector stations, the latter being located at equal distances a art and arranged in the arc of a circle w ose center coincides with the oint of maximum accuracy in the zone of re, measuring the difference in time of arrival at three or more of these stations, and employing this data in connection with the known rate of pulse travel in a liquid medium to determine the point of pulse origin with reference to a target of known location.

26. A method of subaqueous artillery fire reducing a pressure pulse by means of pro] ectile impact with a liquid medium, such pulse being characterized by its brief duration and extensive amplitude, indicating the arrival of this pulse at a series of submerged detector stations, the latter being located at equal distances' apart and arranged in the arc of a circle whose center coincides with the point of maximum accuracy in the zone of. fire, measuring the difierence in time of arrival at three or more of these stations, employing this data in connection with the known rate of pressure pulse travel in a liquid medium to determine the point of pulse origin, plotting the course of a moving target and corelating the point of pulse origin with reference to the location of the target to efi'ect an adjustment of artillery fire. k

27. A method of subaqueous artillery fire adjustment consisting in producing a pressure pulse, characterized by its brief duration and extensive amplitude, electro-mechanically indicating the arrival of such pulse at a series of submerged detector stations, measuring, the difference in time of arrival at three or more of these stations, employing this data in connection with the known rate of pulse travel in the liquid medium to determine the point of pulse origin, plotting the course of a moving target and corelating thepoint of pulse origin with ref- ;erence to the location of the target to effect an adjustment of artillery fire.

28. A method of the character described consisting inp'roducing a characteristic pressure pulse at a predetermined point in a fluid media and utilizing the effect of such pulse on devices responsive thereto for the purpose of determining the-location of said point.

29. A subaqueous method of artillery fire adjustment comprising production of a characteristic pulse in a fluid medium and utilization of said pulse to determine the origin, said pulse being of brief duration, having a circular wave front of considerable amplitude and being capable of travelling long distances without distortion or absorption.

3:0. A subaqueous method of artillery fire ad] ustment comprising utilization of a characteristic pulse produced by an object strikmg a fluid medium to determine the point of its impact, said pulse being of brief duration, havlng a circular wave front of considerable amplitude and being capable of travelling iong distances without distortion or absorp 3 1. A subaqueous method of artillery fire ad] ustment comprising generation of a pulse by means of a projectile striking a fluid medium, determination of the point of projectile impact through the instrumentality of said pulse, said pulse being of brief duration, having a circular wave front of considerable amplitude and being capable of travelling iong distances without distortion or absorp- 1on. V l

32. A subaqueous method of fire adjustment comprising, a determination of the dium by utilization of the resulting charac-- teristic pulse, said pulse being of brief duration and having a circular wave front of considerable amplitude and being capable of travelling long distances without distortion or absorption. I

33 A method of the character described consisting in producing a characteristic pressure pulse at a predetermined point in a fluid medium and utilizing the effect of such pulse for the purpose of determining the location of said point, said pulse being of brief duration 'havlng circular wave front of. considerable amplitude and being capable of travelling long distances without distortion or absorption.

34. A method of the character described consisting in producing a characteristic pressure pulse at a predetermined point. in a given medium and utilizing the efiect of such pulse on devices responsive thereto, for the purpose of determining the location of said point, said pulse being of brief duration,

tion.

EDWARD B. STEPHENSON. 

